1. Field of the Invention
This invention relates to a wallbox-mountable face plate assembly and, more particularly, to an assembly that includes a three-piece mounting arrangement.
2. Description of the Related Art
Wallbox-mountable electrical controls are well known and in widespread use. In many cases, these controls are simple toggle switches to turn on and off lights, or other electrically-powered devices, or both. In other cases, the control in the wallbox is a dimmer, which can continuously vary power to a load, typically a lighting load or a motor.
A variety of face plate assemblies have been designed to cover the wall box and wiring, while still permitting access to the electrical control. A plate with a rectangular slot is a simple configuration often used with a toggle switch. More complex configurations have been designed to serve various functional or aesthetic considerations.
An assembly for use with a push-button switch was disclosed in U.S. Pat. No. 2,740,873, issued Apr. 3, 1956, to K. P. Cronk. That assembly comprises a backing plate, which supports an electrical switch, and a face plate, which covers and attaches to the backing plate. The backing and face plates have openings to accommodate a button that operates the switch. The face plate is held in place on the backing plate by pins that are invisible from the exterior.
A touch switch assembly that likewise has a face plate whose mounting means are not visible from the front of the plate was disclosed in U.S. Pat. No. 4,563,592, issued Jan. 7, 1986 to S. J. Yuhasz et al.
A push-button light switch sold under the "Jung" name, in Germany, comprises a mounting plate assembly that includes flexible snaps to connect with mating members on a cover plate/push-button.
An assembly designed for use with a linear slide dimmer is disclosed in copending U.S. application Ser. No. 032,484, filed Mar. 30, 1987, for a Two Piece Face Plate for Wall Box Mounted Device, incorporated herein by reference. That application discloses a cover designed for use with a particular type of wallbox-mounted electrical control that has an integral yoke plate with a shallow insulating escutcheon protruding from its front surface (i.e., the surface away from the wallbox).
Another linear slide dimmer assembly is the NOVA.RTM. dimmer, sold by Lutron Electronics Co. That assembly includes a metal yoke that mounts to a wallbox, a slide that moves between rails on the yoke, and a faceplate that has, on its back surface (facing the wallbox), snaps that connect to the rails.
As was discussed above, many of the assemblies of the prior art permit the use of a face plate that snaps onto an adjoining member; however, they all require structural elements on the interior of the rear surface of the face plate to connect with corresponding connecting elements on the adjoining member. The need for these elements on the face plate members complicates their fabrication.